Asexual Reproduction/Transcript
Transcript Text reads: The Mysteries of Life with Tim & Moby Tim and Moby are seated at their dining table in the morning. Moby has a sandwich on his plate, and Tim also has one on another plate, but his glass doesn't have any milk. TIM: Can you reach the milk? Moby's hand suddenly comes off and hops away. The camera cuts to a shot of the hand grabbing a carton of milk. The hand puts the milk beside Tim, and fixes itself back on Moby. TIM: Uh... thanks. Tim reads a letter. TIM: Dear Tim & Moby, do bacterias have males or females? From, Gerri. MOBY: Beep. TIM: It's not a riddle, Moby. Bacteria don't have males and females. They reproduce asexually, meaning without sex. Moby holds his hands over his mouth and giggles. MOBY: Beep. TIM: Okay, have your laugh. Asexual reproduction is pretty common among plants and simple animals. In some plants, like the strawberry, a stem extends away from the parent plant with child plants growing all along it. An image illustrates the reproductive method of a strawberry plant as Tim describes it. TIM: Aspen and poplar trees do the same thing with their roots, shooting them out in all directions to grow new trees. A single grove of trees like these might all come from one parent. An image shows the interconnected root system of several aspen trees. TIM: Farmers have asexually reproduced plants for thousands of years by taking cuttings from one and replanting them. An image shows a farmer in ancient times removing a branch from a plant with a knife. TIM: However asexual reproduction is done, the children plants are always genetically identical to the parent plant. So they're actually clones. An image shows the strawberry plant again with its children plants. Over the parent and children plants are circles showing they all have identical DNA. TIM: Clones share the same genetic information, so the parent is basically a twin of the offspring. MOBY: Beep. TIM: In sexual reproduction, a female egg cell is fertilized by a male sperm cell. Each cell contains a half-set of the parent's chromosomes, the structures that contain our genes. When the two cells combine, the genes do too, making a unique new individual. An animation shows sperm cells penetrating an egg. The genes from the sperm and the egg combine. TIM: But in asexual reproduction, the parent's genes simply replicate, then split in two. An animation illustrates how the genes in a single-celled organism split in half. TIM: The process is similar to cell division in eukaryotes. Those are organisms with nuclei in their cells, like plants and animals. An animation the process of cell division for a eukaryote. The DNA in the nucleus replicates and separates in to two nuclei. Then the cell splits in half, creating two cells. Each cell has its own nucleus with a complete set of DNA. Cell division goes on all the time in your body; it's how you grow! TIM: In prokaryotes, single-celled organisms with no nuclei, cell division is reproduction. The entire organism divides through a process called binary fission. Bacteria are prokaryotes that reproduce this way. An animation shows a one-celled organism with no nucleus. It divides into two through binary fission. TIM: Some organisms can reproduce asexually by a neat little process called budding. In budding, a child develops as a growth on the parent’s body. An animation illustrates shows a hydra developing a growth that resembles the parent hydra. MOBY: Beep. TIM: In some organisms, like the hydra here, the bud falls off and becomes an independent creature. The small hydra bud falls off and drifts away from the parent. TIM: In others, like corals, the buds stay put, just one more clone rooted to the entire colony. An animation shows a slowly growing undersea coral. An inset shows how the individual buds stick together to form a larger colony. TIM: And you've probably heard about how a starfish that gets its arm cut off will grow back a new one. That's a process called regeneration, which in certain cases is a form of asexual reproduction. An animation shows a starfish growing a new arm. TIM: Like, if an injury is severe enough, the animal can regenerate into two or more separate children. An animation shows a sponge regenerating into two separate sponges. Tim is doing dishes in the kitchen sink. Moby tears a kitchen sponge into two pieces. MOBY: Beep. TIM: Yeah, I don't think that sponge will regenerate. MOBY: Beep. TIM: Well, it's made of plastic. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts